Plasmapheresis is a common medical procedure whereby plasma is separated from whole blood. The whole blood is comprised principally of cellular components, i.e., red blood cells, white blood cells and platelets. Plasma is comprised largely of water, as well as proteins and various other non-cellular compounds, both organic and inorganic. Continuous plasmapheresis is a process of continuously removing whole blood from a subject, separating plasma from the blood, and returning the plasma-depleted blood to the subject in a continuous extracorporeal circuit. The blood can be returned to the body with replacement fluids, such as fresh plasma and/or an albumin solution. Plasmapheresis is currently used to obtain plasma for various reasons, including transfusion, preparation of fresh-frozen plasma, subsequent fractionation to obtain specific proteins such as serum albumin, cell culture media, and disease therapies involving either the replacement of plasma or removal of specific disease-contributing factors from the plasma.
When treating patients with therapeutic plasmapheresis, a catheter is typically placed in a large vein, such as in the arm, and a second catheter is placed in another vein, such as a vein in the foot or hand. Blood then passes out of the body via the catheter and through a separator. Plasma is separated from the whole blood. The blood without plasma, the desired fluids, and optional replacement fluids can be returned to the body via the second catheter. For plasma donations, automated plasmapheresis equipment is often used where a single venipuncture is required, as the blood is removed and returned through the same site.
There are several different types of therapeutic plasmapheresis including: (i) plasma exchange in which plasma that is separated and discarded is replaced with fresh plasma or an albumin solution, (ii) double filtration plasmapheresis in which plasma is passed through a separator with a small pore size so as to selectively remove large molecular weight proteins, or (iii) plasma adsorption in which plasma flows into a plasma adsorption column wherein certain substances can be adsorbed and removed. Plasmapheresis used for plasma donations typically uses centrifugation (e.g., Haemonetics blood processing systems) or centrifugation with a simple filter (e.g, Fenwal blood processing systems).
Numerous factors, including cardiac output, peripheral resistance, blood vessel elasticity, and blood volume, can affect a person's blood pressure (BP). The volume of plasma removed during plasmapheresis (e.g., 690-880 mL) is consistent with minimal physiological changes due to hypovolemia. However, the effect of plasmapheresis on blood pressure has rarely been reported. A treatment regime in which periodic plasmapheresis can be used to treat blood pressure disorders would be desirable.